ON EXCHANGE MECHANISM IN HG1-XMNXS

The magnetic susceptibility of Hg0.95Mn0.05S and Hg0.90Mn0.10S was mea sured by the SQUID technique. The experimental data were compared with the extended nearest neighbour pair approximation (ENNPA) calculation . The long range exchange interaction J = J(NN)R(-n), with the exponen t n = 4, was found for both samples. The nearest neighbour exchange in tegral J(NN) was found to be around two times smaller than the effecti ve exchange integral J(eff). The small value of the exponent n, which is a characteristic of the narrow gap semimagnetic semiconductors (SMS C's), as well as the small J(NN)/J(eff) ratio, show the importance of a long-range exchange mechanism.